Undergraduate Intern: Mara Minner - University of California, Berkeley

maraminner@gmail.com

Faculty Mentor: Professor Stephen A. Mahin Post-Doctoral and Graduate Mentors: Jiun-Wei Lai and Barb Simpson

Research Conducted at the University of California, Berkeley

Introduction

Methods

• Prototype Building: The prototype building design selected for this study is a 3-story office building designed by

Troy Morgan (2008) modified to contain four identical NCBFs shown in Figure 5. For

comparison, Figure 6 displays the special concentrically braced frame (SCBF) featured in the

original design of this prototype building, which is used in the comparison of the building

performance of the NCBF and SCBF. Each story is 15 ft in height, and has a rectangular

footprint that is 120 ft by 180 ft, with 30 ft bays, shown in Figure 7.

• 2D OpenSees Model: A total of 240 dynamic analyses were performed using:

Story drift ratios, floor velocities, and floor accelerations were recorded. MATLAB was used to

post-process the data by extracting peak parameter values and performing a collapse mode

assessment.

• PACT Model: The Performance Assessment Calculation Tool (PACT) is a computational tool developed by

the Applied Technology Council (ATC) that measures performance in terms of:

repair and replacement costs

the probability of incurring casualties

repair time

the probability of unsafe placarding (ATC, 2012).

A PACT intensity-based assessment was performed for the NCBF prototype building and

repeated for an SCBF system, using the same prototype building but with an SCBF lateral

load-resisting system.

Results

Conclusions General trends in the PACT results indicate that an SCBF building would generally be

expected to outperform an NCBF building in terms of:

• Repair cost

• Repair time

• The probability of unsafe placarding.

Figure 2: Complete

fracture of gusset plate

(Lignos, 2011)

Figure 3: Local buckling

of square HSS brace

(NISEE, 1994)

Figure 4: Global

buckling of braces

(AIJ, 1995)

Acknowledgements This research was organized by the Pacific Earthquake Engineering Research (PEER) Center

as part of the 2013 Internship Program with financial support provided by the National Science

Foundation (NSF). The author would like to thank Professor Stephen Mahin for his invaluable

direction and overall geniality during the program. Additionally, the author is deeply grateful for

mentors Jiun-Wei Lai and Barb Simpson for their guidance, encouragement, patience, and

willingness to answer an interminable number of questions throughout the research process.

Much appreciation is likewise directed towards Heidi Tremayne, the coordinator of the PEER

Internship Program, for her never-ending effort and commitment to making this program a

success.

References AIJ. (1995). “Reconnaissance Report on Damage to Steel Building Structures Observed from

the 1995 Hyogoken-Nanbu Earthquake”, Architectural Institute of Japan.

ATC. (2012). “Seismic Performance Assessment of Buildings Volume 1 – Methodology.”

Applied Technology Council, Redwood City, CA. [electronic version:

https://www.atcouncil.org/files/FEMAP-58-1_Volume%201_Methodology.pdf]. Lignos, D. (2011). Tohoku Japan Earthquake & Tsunami Clearinghouse. EERI. Retrieved August 15,

2013 from http://www.eqclearinghouse.org/2011-03-11-sendai/2011/08/03/eeri-steel-

structures-reconnaissance-group/pgarage-gussetfracture/.

Morgan, T. (2008). “Summary of Design Basis for 3-Story NEES-TIPS Model Buildings.”

Forell/Elsesser Engineers, San Francisco, CA.

NISEE, e-library. (1994). “Tube fractured due to local buckling.” Date Accessed: August 2013.

<http://nisee.berkeley.edu/jpg/5074_1631_0641/IMG0027.jpg>. UBC. (1988). Uniform Building Code. International Conference of Building Officials, Whittier, CA.

Future Work To continue this research effort, additional PACT analyses can be performed investigating

other details of the NCBF system. PACT can also be used to assess the performance of other

systems, such as the ordinary concentrically braced frame (OCBF). Additionally, upon

completion of an experimental study, retrofit strategies should be explored based on the failure

modes that are observed.

to NCBFs after past earthquakes. Performance-based measures are necessary for owners

of existing NCBFs to make informed decisions about possible retrofit strategies. This project

seeks to analyze the performance of a prototype NCBF building, assessing the expected

repair costs, repair time, casualties, and probability of unsafe placarding following various

intensities of seismic activity. The results of the analysis are compared to those of an SCBF

system.

Many existing buildings have lateral load-resisting

systems utilizing steel concentrically braced frames

designed using codes prior to the 1988 Uniform Building

Code (UBC, 1988). Due to differences in detailing, as

displayed in Figures 1a and 1b, the ductility of NCBFs is

considerably lower than that of modern special

concentrically braced frames (SCBF). As a result, the

seismic safety of older NCBF buildings is likely lower

than that of current AISC-compliant SCBF buildings, and

older NCBF buildings may be vulnerable to collapse in

response to seismic activity. Figures 2-4 display damage

Figure 1a: SCBF

connection

Figure 1b: NCBF

connection

Figure 5: NCBF Figure 6: SCBF

Figure 7: Floor plan

Figure 8: Comparison of

repair costs

Figure 9: Comparison of

repair time in parallel

Figure 10: Comparison of

repair time in series

Figure 11: Comparison of

probability of unsafe

placarding

Figure 12: Comparison of

injuries

Figure 13: Comparison of

deaths

3 Hazard Levels: • 50%/50 years

• 10%/50 years

• 2%/50 years

2 Earthquake Directions: • Fault Normal

• Fault Parallel

40 Ground

Motions

PACT